[INTERNAL] Project.md: Use default instead of non existing main branch

Fixes #994

Author: flovogt

docs/pages/Project.md

@@ -15,7 +15,7 @@ The source directory of an application (typically named `webapp`) is mapped to t
 An applications source directory may or may not contain a `Component.js` file. If it does, it must also contain a `manifest.json` file. If there is a `Component.js` file, an optimized `Component-preload.js` file will be generated during the build.
 
 ### library
-UI5 libraries are often referred to as reuse-, custom- or [control libraries](https://github.com/SAP/openui5/blob/main/docs/controllibraries.md). They are a key component in sharing code across multiple projects in UI5.
+UI5 libraries are often referred to as reuse-, custom- or [control libraries](https://github.com/SAP/openui5/blob/-/docs/controllibraries.md). They are a key component in sharing code across multiple projects in UI5.
 
 A project of type `library` must have a source directory (typically named `src`). It may also feature a "test" directory. These directories are mapped to the virtual directories `/resources` for the sources and `/test-resources` for the test resources.